1. Field of the Invention
This invention relates to a control device and method for an automatic transmission for automatically shifting a synchromesh type gear transmission.
2. Description of the Prior Art
A first conventional control device for an automatic transmission is adapted to automatically shift the gear position of a synchromesh-type gear transmission. In an exemplary case in which the gear position is shifted from fifth gear to third gear, as shown in the flowchart of FIG. 12 and the time chart of FIG. 9(A), the gear position is first shifted from fifth gear to fourth gear, and then from fourth gear to third gear.
A second conventional control device for an automatic transmission adopts a different approach for the case in which the gear position is shifted from fifth gear to third gear. That is, as shown in the flowchart of FIG. 13 and the time chart of FIG. 9(B), the gear position is shifted directly from fifth gear to third gear, while fourth gear is skipped. In other words, making use of a H-shaped shift pattern, the neutral state is detected to thereby shift the gear position to third gear in a single stroke.
When the first conventional control device for an automatic transmission sequentially effects shifting from fifth gear to fourth gear and then to third gear, a relatively light load acts on the synchronizer. However, due to an increased number of shift operations, the first conventional control device has a drawback of increased overall shift time.
When the second conventional control device for an automatic transmission effects shifting directly from fifth gear to third gear, while skipping fourth gear, the reduced number of shift operations shortens the overall shift time. However, the second conventional control device has drawbacks in that the synchronizer requires a relatively long synchronization time, due to large relative rotation which results from a great change in gear ratio and in that when the synchronization time of the synchronizer is shortened, a larger load acts on the synchronizer, adversely affecting the service life of the synchronizer.
In order to reduce the load, the second conventional control device for an automatic transmission may prolong the shift time through a reduction in shift speed. However, in this case, the second conventional control device encounters a problem that the efficiency becomes lower than that achieved by the first control device.
It is a general object of the present invention to provide a control device and a control method for an automatic transmission for automatically shifting a synchromesh type gear transmission which achieves reducing the load acting on the synchronizer to thereby increase service life and decreasing the number of shift operations to thereby shorten the overall shift time.
It is another object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission in which when shifting from a certain gear to another gear is effected while skipping an intermediate gear, the shifting is performed after temporary synchronization is effected by use of a synchronizer of the intermediate gear.
It is still another object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission, which comprises a controller in which shifting to another gear is performed after temporary synchronization is effected by use of a synchronizer of an intermediate gear between one gear and the another gear, when shifting from the one gear to the another gear while skipping at least a next gear of the one gear is effected.
It is a further object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission in which the skip shift is judged through detection of a shift instruction.
It is a still further object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission, in which the skip shift is judged through comparison between the one gear and the another gear based on the detected shift instruction.
It is a further object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission, in which the temporary synchronization by means of the synchronizer of an intermediate gear is realized through partial synchronization of the synchronizer of the intermediate gear.
It is a still further object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission, in which the temporary synchronization by means of the synchronizer of the intermediate gear is partial synchronization which is realized through adjustment of the load for engagement of the synchronizer of the intermediate gear.
It is a yet further object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission, in which the partial synchronization is half of ordinary synchronization performed during shifting.
It is a yet further object of the present invention to provide a control device for an automatic transmission for automatically shifting a synchromesh type gear transmission, in which when two or more intermediate gears between the present gear and the another gear are to be skipped during the skip shift, the intermediate gear which is closer or closest to the center in terms of gear ratio is selected, and the temporary synchronization is performed by use of the synchronizer of the selected intermediate gear.
It is a yet further object of the present invention to provide a control method for an automatic transmission for automatically shifting a synchromesh type gear transmission, wherein when shifting from a certain gear to another gear while skipping an intermediate gear is effected, the shifting to the another gear is performed after temporary synchronization is effected by use of a synchronizer of the intermediate gear.
The present invention provides an automatic transmission for automatically shifting a synchromesh-type gear transmission wherein comprises a controller in which shifting to another gear is performed after temporary synchronization is effected by use of a synchronizer of an intermediate gear between one gear and the another gear, when shifting from the one gear to the another gear while skipping at least a next gear of the one gear is effected. Therefore, the present invention achieves the effect of reducing the load acting on the synchronizer to thereby increase service life and the effect of decreasing the number of shift operations to thereby shorten the overall shift time.
In the present invention, the skip shift is judged through detection of a shift instruction. Therefore, the present invention achieves the effect of the skip shift being judged easily.
In the present invention, the skip shift is judged through comparison between the one gear and the another gear based on the detected shift instruction. Therefore, the present invention achieves the effect such that the synchronizer of an intermediate gear to undergo temporary synchronization is selected reliably.
In the present invention, since the temporary synchronization by means of the synchromesh mechanism of the intermediate gear is realized through partial synchronization of the synchromesh mechanism of the intermediate gear, the transmission is shifted to the another gear after the relative rotation has been reduced reliably. Therefore, the present invention achieves the effect of mitigating load acting on the synchronizer to thereby increase service life.
In the present invention, since the temporary synchronization by means of the synchromesh mechanism of an intermediate gear is partial synchronization which is realized through adjustment of the load for engagement of the synchromesh mechanism of the intermediate gear, the transmission is shifted to the another gear after the relative rotation has been reduced to a proper level. Therefore, the present invention achieves the effect of mitigating load acting on the synchronizer to thereby increase service life.
In the present invention, since the partial synchronization is half the synchronization performed during ordinary shifting, the transmission is shifted to the another gear after the relative rotation has been reduced to a proper level which is half the relative rotation encountered during ordinary shifting. Therefore, the present invention achieves the effect of mitigating load acting on the synchronizer to thereby increase service life.
In the present invention, when two or more intermediate gears between the one(present) gear and the another gear are to be skipped during the skip shift operation, the intermediate gear which is closer or closest to the center in terms of gear ratio is selected, and the temporary synchronization is performed by use of the synchromesh mechanism of the selected intermediate gear. Therefore, the transmission is shifted to the another gear after the relative rotation has been reduced to a practical and optimal level. Thus, the present invention achieves the effect of restraining load acting on the synchronizer to thereby increase service life.